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They have many different uses:

Raising or lowering a water bucket.

Telling the time by moving its cogwheels or gears.

Moving people from one place to another.

Entertaining children in a park by swinging.

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All of them are made of mechanisms

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Mechanisms are devices that transmit and/or

convert forces and motions from an input

element to an output element.

The aim of a mechanism is to make the tasks

easier with less effort and more comfort.

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Input motion

Input force

Mechanism Output motion

Output force

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Classification of mechanisms

To transmit motion

Linear Rotary

To transform motion

From rotary to linear

From rotary to reciprocating

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Linear

Lever

Pulley

Rotary

Friction drives or wheels

Pulleys with belts

Gear mechanisms

Gear mechanisms with chain

Worm gear

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A lever is the simplest kind of mechanism. Common

examples of each type are the crowbar, the

wheelbarrow and the pair of tweezers.

Parts: The load is the object you are trying to move.

The effort is the force applied to move the load.

The fulcrum (or pivot) is the point where the load is pivoted.

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M.A. = Effort

Load

Load

Effort

Fulcrum

d1

d2

Law of the lever

L·d1 = E·d2

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The longer the distance is, the less effort you have to do1

Balanced lever

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1st class

M.A.?

2nd class

M.A.

3rd class

All levers are one of three types, usually called

classes. The class of a lever depends on the

relative position of the load, effort and fulcrum T

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http://www.youtube.com/watch?v=Us2KfO_yrPA

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It is a wheel that turns when a rope, belt or chain passes through a channel.

It rotates around an axle that is fixed

when you apply a force (F) to move up a load (R).

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Fixed pulley

E=R

No mechanical advantage

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Moveable pulley

E=R/2

Mechanical advantage=2

The force you apply is multiplied

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Compound pulleys

Mechanical advantage=R/F

The force you apply is multiplied

4:1

6:1

It is a set of fixed and

movable pulleys.

The more movable

pulleys, you have the

less effort you have to

apply

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https://www.youtube.com/watch?v=9T7tGosXM58&feature=related

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This mechanism is made up (consists) of at least

two wheels or pulleys in contact.T

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Driver wheel

Driven wheel

Shaft

•If the number of wheels is odd, the drivenwheel rotates in the same direction than thedriver wheel.•If the number of wheels is even, the drivenwheel rotates in the opposite direction thanthe driver wheel.

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A pulley system is made up of two pulley wheels each

on a shaft, connected by a belt. This transmits rotary

motion and force from the driver pulley to the driven

pulley.

driven pulley rotates in the same direction driven pulley rotates in the opposite direction

BeltAndPulley

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Gears are wheels with teeth. Gears consist of

toothed wheels fixed to shafts. The teeth

interlock with each other, and as the first shaft

(the driver shaft) rotates, the motion is

transmitted to the second or driven shaft so they

are used to transmit movement between two

shafts.

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A number of gears connected together are called a

gear system or gear train

They can also be moved with a chain. It´s also

called sprocket.

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It’s a mechanism made up

(composed) of a gear and a worm

(threaded shaft). It’s a method of

making large speed reductions.

Each time the shaft spins one

revolution, the gear turns forward

by only one tooth.

The worm can drive the worm gear

round, but the worm gear cannot

drive the worm, so it’s used as a

breaking system. Worm gear, worm

gear (video)

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The quotient of the speed/velocity is called the gear ratio.

The gear ratio also determines the amount of turning force or torque transmitted.

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Rotary into Linear

Rack and Pinion

Nut and bolt

Winch with a crank handle

Rotary into Reciprocating

Cam

Crank link slider

Crankshaft

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The pinion is a round gear and the rack is a flat

bar with teeth.

It is a reversible mechanism.

Rack and pinion

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It’s a reversible mechanism

you can spin both, the nut

or the bolt.

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The longer the crank handle is, the less force you

need to move the load.

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The cam is a flat piece of metal that has a

specific shape that pushes the follower.

Different types of cams

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It’s made up of a circularcrank, a link (connectingrod) and a slider.

It is a reversible mechanism.

Crank link slide

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The crankshaft is the red part of the figure.

It is a reversible mechanism.

Crankshaft video

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